EP 253738 describes taxol derivatives bearing hydroxyls in positions 10 and 7 and a keto in position 9, which derivatives can be substituted by a isoserine residue in position 13; WO 94/25441 discloses anthrapyrazolones which can be used as anticancer agents, and a process for their synthesis; the "Journal of the American Chemical Society", vol. 93 No. 9, pages 2325-2327, reports the isolation and characterization of taxol derivatives having tumor inhibitory properties.
The novel compounds contain a pyrazoline group involving the C.sub.7 and C.sub.9 carbons. The esters at C.sub.13 with isoserine chains functionalized at C.sub.3 ' and at NH have cytotoxic activity on the cell lines of the most common-human tumors as well as in vivo anti-cancer activity. The compounds of the invention are potent cytotoxic agents, particularly active on cells resistant to known antiblastics and are strong apoptosis inducers on these cell lines, which activity is significantly important in the oncologic therapy.